Mobile or wireless communications networks are capable of carrying circuit-switched and packet-switched traffic (e.g., voice traffic, data traffic, etc.) between mobile stations and other endpoints, which can be another mobile station or an endpoint connected to a network such as a public-switched telephone network (PSTN) or a packet data network. Traditional wireless protocols provide for circuit-switched communications, such as the circuit-switched protocol provided by 1×RTT, defined by CDMA 2000. With circuit-switched communications, a dedicated circuit or channel is established between nodes and terminals to allow communication between endpoints. Each circuit that is dedicated cannot be used by other users until the circuit or channel is released.
In contrast, with packet-switched communications, data is split into packets, with the packets routed individually over one or more paths. A widely-used form of packet-switched communications is defined by the Internet Protocol (IP). Examples of packet-switched communications that are possible over data networks include electronic mail, web browsing, file downloads, electronic commerce transactions, voice or other forms of real-time, interactive communications, and others. To enable the establishment of packet-switched communications sessions in a network, various control functions (implemented with software and/or hardware) are deployed in the network. Some standards bodies have defined subsystems within communications networks that include such control functions. One such standards body is the Third Generation Partnership Project (3GPP), which has defined an Internet Protocol (IP) multimedia subsystem (IMS) that includes various control functions for provision of IP multimedia services, including audio, video, text, chat, or any combination of the foregoing.
In the 3GPP2 context, the equivalent of the IP multimedia subsystem is sometimes referred to as a multimedia domain (MMD) network. The term “multimedia network” is used to generally refer to any one of an IP multimedia subsystem, MMD network, or any other network in which multimedia communications (any one or more of video, audio, text, chat, e-mail, web browsing, etc.) are possible.
To provide wireless access to a multimedia network, a wireless access network according to any of the following standards can be used: 1×EV-DO or 1×EV-DV (which are defined by the CDMA 2000 family of standards), WiFi (which is a wireless local area network or WLAN technology defined by the IEEE 802.11 specifications), and WiMAX (Worldwide Interoperability for Microwave Access) (which is also a WLAN technology defined by the IEEE 802.16 specifications). Note that 1×RTT also provides packet-switched communications, in addition to circuit-switched communications.
It is common for circuit-switched access networks (such as those based on 1×RTT) to coexist with packet-switched access networks for multimedia networks. Certain mobile stations are able to operate with both circuit-switched wireless access networks and packet-switched wireless networks. Such mobile stations are referred to as multi-mode mobile stations or multi-mode handsets.
Conventionally, when a multi-mode mobile station transitions between a packet-switched wireless access network and a circuit-switched wireless access network, the set of services provided to the multi-mode mobile station changes. When attached to the packet-switched access network, nodes (e.g., application servers or other nodes) in the multimedia network (part of a packet-switched service domain) provides services to the mobile station. However, when the mobile station transitions to the circuit-switched access network, services to the mobile station are provided by nodes in the circuit-switched service domain.
As a result, when a multi-mode mobile station transitions between a circuit-switched access network and a packet-switched access network, the services provided to the multi-mode mobile station will be interrupted since the provider of the services will have to switch to a different service domain.